Answer:
The correct answer is D.
Explanation:
The stages of sleep are divided in REM and NREM, also the NREM stages are divided in 1, 2, 3 and 4.
In stages NREM 3 and 4 occurs the deeper sleep and the person is less likely to be awaken during these stages.
In stages 1 and 2 occur the lighter sleep.
In REM stage the person is in a state very similar to the awake state and therefore is more likely to be awaken in this stage. Also, in the REM stage occur dreams.